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Keep program running

February 14, 2019, 1:59 am
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Hello, i'd first like to apologize for this very beginner-like question... Im very new to labview and i'm starting to see the potential and liking it, but i'm having troubles so far.

 

I have this piece of hardware that i'd like to control with LabVIEW and the pieces of code i've constructed works, but the program terminates when i've pressed both of my buttons? 

 

I have two event sctructures that react when mouse is down on two different buttons, the blocks inside the eventstructure is executed as they should etc.

 

The problem is that when i've pressed both my buttons, the program terminates. I'd like to add more code to be done afterwards. And it seems i'm not able to run the same event structures twice? I can't push the button again, it goes dark and stays dark. (After i press it first time it switches back, it is after i press 2nd time it stays dark). 

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Difference between running continuously and While loop

February 14, 2019, 2:16 am
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Hi All

 

Is there any Difference between running continuously and While loop apart from Conditional terminal in while loop?

 

 

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Referencing other packed libraries within a packed library

February 14, 2019, 6:19 am
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How would you go about referencing a PL inside another PL without creating a copy of the referenced PL when building?

 

I have a PL1 that is used by PL2. PL2 is used directly and so is PL1 so when LV builds an executable I assume PL1 gets included twice even though (in this instance) they are the same version.

 

Found the solution for this part:

FQ6xg8VDPd.png

 

I can see some potential problems with doing this, namely the referenced PL is rebuilt and no longer compatible, but are there any ways to overcome this?

 

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How to correctly set up instrument queues for LabVIEW instances from different machines

February 14, 2019, 7:15 am
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This is probably a bigger step than my LV knowledge allows me to take, but recently this problem has arised in the lab.

 

We are sharing several instruments, each with a number of channels, between experiments. To make two representative examples:

  • one is a 4-channel oscilloscope with its LV drivers, which is connected via LAN to a local network (so it's directly accessible by every PC in the lab);
  • one is a NI PXIe chassis with four PXIe cards, connected via a serial cable to one of the PCs.

Each experiment controls two oscilloscope channels and two PXIe cards (there's more, but the other instruments work the same way), and is run by a different PC.

 

Now, I already experienced problems when two VIs on the same machine called the same instrument at the same time, causing a timeout error. I can imagine that adding another computer, which runs a different LV version, only makes things worse.

 

I've read about queues, producer/consumer loops, but I don't really know which is better suited to our needs, and I haven't really understood well how they work (so far my "expertise" with LV is limited to event structures in a while loop - is that a state machine?)

 

I thought about having only one computer (the one connected to the PXIe chassis) control all the instruments (even the LAN-controlled ones), and the experiments VIs talk to it via TCP (or using global variables, if it's the same computer?). Should I have a separate VI for each instrument or is there a way to do it in a more efficient way?

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dynamically run VI not working after built

February 14, 2019, 9:05 am
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Hi all, am trying to build an application that allows a user to select a VI(strict typedef) to run.

My code works in the development environment but refused to run after I compiled it.

Please see as attached.

 

 

Can you help to advise what can I do to make them run?

 

Thank you

 

Regards,

Stonewall

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"Breakeven point" for using AMC messages vs. FGVs to send/receive data

February 14, 2019, 9:54 am
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Hi all,

 

I'm using LabVIEW 2016. I have a medium-sized application where I'm using AMC (asynchronous messaging communication) library to send and receive messages and data between multiple local threads (VI's on the same machine). 

 

Initially I used a lot of FGVs to send data to the UI thread from other threads for display, keeping the UI thread free of incoming messages. The FGVs are read in the timeout case (timeout=10ms) of event structure in the UI thread. Then I got a suggestion to use messages in the UI thread as well to maintain consistency and to reduce CPU usage due to repeated reading of FGV data every 10ms. The rationale was that the asynchronous messages would theoretically be processed only when received, not necessarily every 10ms. (The fastest rate in the application is currently 25ms, which could change later depending on system changes).

 

So far I don't see the benefit of using messages in the UI thread in terms of reducing CPU usage. I'm thinking the overhead of flattening/unflattening from/to XML in the messages is adding to CPU usage, that I can get rid of using FGVs. 

 

Is there such a thing as a "breakeven point" of say, number of individual messages or number of individual data packets (i.e. 1D array, 2D array, etc) when you might say "less than 10 -- use messages, more than 10 -- use FGVs".

 

Sorry, uploading code is not feasible, but I think this is a pretty general topic.

 

Would appreciate any pearls of wisdom on this issue! Smiley Happy

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LabVIEW Development Environment Crashes When Uploading to a cRIO-9057

February 14, 2019, 10:17 am
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I have a labview project that uses a cRIO-9057. When I make a change to my real time VI and upload it, my labview development environment crashes as soon as the progress bar on the "Deployment Progress" window finishes.

lv crash screen.png

However, once I re-start LabVIEW and re-upload my VI to my cRIO, everything works fine. I can stop and start the VI as many times as I like until I save a change to my VI, then LabVIEW will crash again as soon as I try to upload my code.

 

I have not had this issue with other labVIEW projects on this cRIO. I have tried formatting my cRIO and deleting and re-creating my project (although not my individual VIs), but this has not helped. Is this a known issue? What else can I try?

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Continuous TCP Transfer

February 14, 2019, 11:48 am
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Hello, 

 

I am trying to make 2 LabView Vi's detect when a change is made in the other.  Here is an example.  A and B are the names of the two VI's which are both running.  If a true/false button is pressed in A, then B will detect it and switch its button as well.  As well, if a button is pressed in B, then A will detect it.  All of the examples I have seen use a server/client system for the TCP connections which I have applied and works well, but this only seems to be a one way transfer system and the server can never detect what is happening in the client.

 

I have attached the attempt I have made in order to detect them, which I can explain a little more about.  First the TCP connection is opened the same way any server/client pairs open.  The server computer sends a cluster of 5 elements which updates continuously.  When a button is pressed in the server (hence the event structure), it is supposed to change the same button on the client computer.  As well after the event, it is supposed to be reading the value of the button press in the client VI.  Is there an easier way to do this, or a way that acts as a two way road instead of having 2 individual 1 way tunnels?

 

Thanks!

 

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NI 9237 Not reading any data in FPGA?

February 14, 2019, 1:49 pm
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I'm just trying to read and send the values I get from a torque sensor (fancy load sensor) in FPGA. I've tried this using just scan interface and It works just fine, but for some reason the data I get returned at all stages of the data acquisition is 0. What could the problem be?

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Continuously collecting strain data from two channels

February 14, 2019, 3:28 pm
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Good Evening,

 

I am a senior in Mechanical Engineering, for our senior project, we need to create a LabVIEW program that will collect strain data continuously as it is subjected to varying loads. Basically, we are instrumenting spinal surgical tools with strain gauges and want to collect a load monitoring system that will inform surgeons how much load they are applying during surgery. We are using the following instruments:

 

1. Two KFH-6-350C1-11L3M3R strain gauges

2. Two NI-9945 quarter bridge completion circuits

3. CompactDAQ Chassis equipped with NI-9237

4. NI EDAQ-9172

 

Long story short, we have two strain gauges attached to the tools and need to collect the strain data continuously, about 3 minutes or so. The tools are subjected to a load of 50 lbs in 5 lb increments using an MTS machine. So, for the DAQ, we have two channels.

 

I have written a code but cannot seem to figure out how to continuously collect the strain data, see attached. Any assistance will be much appreciated. Also, please provide explicit details, as I am still learning LabVIEW and need to understand the process.

 

We are running the raw strain through a low pass filter to remove excess noise of 60HZ.

 

If you need any further information from me, please let me know. I am more concerned with ensuring the LabVIEW code can handle the continuous data collection that the process we are utilizing to collect the strain.  

 

Thank you for your assistance!

 

V/R,

 

JC

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Create new table in MS access through LabVIEW

February 14, 2019, 5:40 pm
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I am trying to create a new table to an existing DB [MS access (. Mdb)]. Is it possible.

 

I have already created a "insert string" in my program (labview 2015) but only inserting it to a single table only that i have created. I wish i can separate the data and sort it by month. 

1 table: 1 month

 

i need a function in my labview program that create a table in MS access. 

 

please advise

thank you in advance

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Implementing a curved motion using LabView

February 14, 2019, 7:13 pm
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Hello all, 

I am learning LabView and want to implement a .vi for our FRC robot to make a curved motion. We are able to calculate the distance to our target but want to approach it within a curved movement rather than a straight line.  

Attached image explains what we need to achieve. Any help or guidance would be highly appreciated.

 

https://www.researchgate.net/figure/Curved-path-to-reach-the-marker_fig11_275229789

 

Thank you.

Jimit

High School Student.

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LABVIEW

February 15, 2019, 2:24 am
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Hi,

I have some dymanic data ,,,i need to check all those data and as per requirement i will take only one data at a time from those dymanic data and use that data in other purpose as a input  ,,how can I implement this in LabVIEW?? 

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FPGA I/O node: you have connected two terminals of different types

February 15, 2019, 4:07 am
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Hi everyone, not long ago I took over a project from a senior. There is a very obvious problem with one labview program that I got --- when it comes to the FPGA I/O nodes, it always warns: you have connected two terminals of different types : .... However, in another different but similar vi，everything is OK. 

To be honest, I am not very familiar with the FPGA I/O nodes and even the labview language. It can't be better if there is someone who would like to give me some tips. 

微信截图_20190215195737.png微信截图_20190215195838.png

 

（I'm sorry that there is something wrong with that computer' USB interfaces and no Internet is available so I have to take the photos）

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horizontal switch

February 15, 2019, 5:06 am
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Dear,

 

I would like to make more user friendly my Labview GUI using few horizontal single pole , dual throw switch as in the picture.

I couldn't find any example from the discussion forum, only for vertical ones.

Any idea is welcome, thanks in advance for help.

 

SPDT_switch.PNGSPDT SWITCH

 

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FIR coefficients

February 15, 2019, 5:21 am
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hi

i'm trying to design FIR filter for DDC. i have tried "Parks-McClellan.vi" and i used only forward coefficient to my FIR and the reverse 0. however there is no coefficeint and my filter just passes the input data with no filtering.

can anyone help please(as im new to labview im sure ive done something wrong)

thanks

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Unknown Network Published Shared Variables Resolution

February 15, 2019, 5:29 am
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Hello,

 

I recently ran into an issue where I had to pull data from a Network Published Shared Variable that is an intricate cluster of clusters, types, arrays, etc...We have numerous versions of this code deployed on hundreds of machines where the type definition deployed in the field changed slightly with each version.  The issue with NPSV's is that if the type definition on the client side doesn't match exactly with that published by the server, it throws: 

 

Error -1950678965 occurred at Read Variable in #####.vi

Possible reason(s):

LabVIEW:  The value read is of a data type that cannot be converted to the data type of this Shared Variable node.

 

I needed code that will work regardless of the version of the server.  It is possible to keep all revisions of the typedef and iterate through them to find one that does not error out, but there is a simpler solution.  Fortunately, the top level type is a cluster and I know that I only needed the 7th element of that cluster.

 

When pulling a NPSV, LabVIEW will allow you to pull it as a variant of any NPSV without error!  Then I just needed to decode the variant.  I found this article that was very helpful:

 

https://forums.ni.com/t5/LabVIEW/Get-a-cluster-element-value-from-a-variant/m-p/3814182/highlight/true#M1077354

 

So here's the code I ended up using:

 

Unknown Network Shared Varible Decoding.png

 

 

This code works for all versions of the deployed code as long as the position of cluster item does not change (it doesn't).

 

I thought this would be helpful for others, future me, and NI Tech support to show how I solved the problem.  Using the VI's in the "Data Type Parsing" palette, same as the "Get Cluster Information.vi", it would be possible to dig through more complex data types if needed.

 

Enjoy!

 

 

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Stop a While Loop Before My Wait Time Elapses in LabVIEW

February 15, 2019, 5:57 am
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Hi guys,

I have a While loop with a long Wait (ms) time function. My Stop button takes too long to stop my loop. How can I program my Stop button to end a while loop immediately? I appreciate  your efforts in answering my question.

 

Kindly check my Project as a snippet.vi.png

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App Builder Strange Behavior

February 15, 2019, 6:18 am
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This isn't really a problem, but it bothers me.  I have a project that contains a library (both attached).  In the build spec, two of the files (Aux Data.ctl, and Step Data.ctl) used to go to a special destination (A separate app needed to load them dynamically).  I changed things so that I no longer needed those 2 files to be deployed in a special location. In the current build spec, they go into the .exe.

Here's what bugs me: several times during the build process, it's hunting for Aux Data.ctl and Step Data.ctl (but not for any of the other .ctl files).  Here is one of the message boxes that is displayed:

hunt.png

It's looking in the .exe. Eventually it finds the files and the build is OK. But why is this happening? I tried recreating the build spec from scratch, but the same thing happens.  What could be causing this?

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problem in Real-Time module labview 2016

February 14, 2019, 7:20 pm
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Hi everyone, i had my labview 2016 and myrio toolkit installed in my computer windows 10. When i want to install the real time module, it prompt me about the NI device drivers. What is the driver actually and where can i get it ? I download the myrio toolkit and this real time module from labview myio software bundle. Please help me, thanks!!

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